The field of this invention is building materials, particularly wooden beams, trusses, joists and girders. The current invention is intended to be used primarily in residential or light commercial construction and other applications where a wooden joist is appropriate.
Increasing costs of lumber and potential lumber shortages have precipitated the need for increased efficiency in the design and use of wooden beams, trusses, joists and girders. Wooden trusses have been used extensively. Chandler discloses a wood truss structure in U.S. Pat. No. 4,001,999, and a wood deck structure utilizing a wood truss in U.S. Pat. No. 3,345,792. Hunt et al. discloses a continuous shear resistant timber girder in U.S. Pat. No. 3,861,109 which uses a truss design including some attached side panels. Price uses a lattice web in his wood truss shown in U.S. Pat. No. 3,702,050. Snider uses discontinuous side panels in his wooden joist shown web glued to the flanges in U.S. Pat. No. 4,074,498.
Construction of steel beams has been made more efficient by cutting an I-beam web along a serrated line and fabricating the beam by welding along the points of the serrations. This is demonstrated by Moyer in U.S. Pat. No. 1,644,940. A fabricated non-symmetrical steel beam is shown by Simpson in U.S. Pat. No. 3,263,387. Harris describes a hollow rectangular sectional metal beam using discontinuous rectangular panel sidewalls in U.S. Pat. No. 2,941,635.
The prior art has problems in several respects. Prior wood truss devices have an overall depth so great in many cases they require an increase to the height of the structure. This in turn increases building costs associated with the increased height which offset or exceed the savings associated with the truss. This problem is especially applicable to floor joists in most light construction. Wood trusses are difficult and relatively costly to fabricate in many instances unless the time and costs associated with a shop production layout are incurred. Special jigs or patterns may be necessary to aid in the cutting, fitting and connecting of truss components. The prior art has also not appropriately optimized the amount of glue surface area required between the tension and compression chords and the truss members. Wooden beams cannot be fabriated by gluing the points of serrated or dentated core halves together because of insufficient glue area. The prior art has also failed to develop optimum means for dissipating the effects of concentrated stresses at the support points in wooden beams. True box type wooden beams heretofore disclosed do not provide usable spaces for running transverse conduit at any point along the entire length of the beam. Staggered placement of the side panel elements has prevented convenient location of transverse runs of conduit or other utility ducts. True box beams also use side panels which are continuous for the length of the beam, requiring excessive amounts of material. Current wooden box beams do not allow passage of conduit, pipes, wires, etc. along the length of the beam because of the occasional placement of vertical spacers. Box beams incorporating relatively large distances between adjacent side panels at one point so that transverse conduits may pass through the opening have reduced strength to resist lateral loading.